The Effect of Rifampin on the Metabolism of Istradefylline in Healthy Volunteers.

Inclusion Criteria:

- Healthy non-smoking male and post-menopausal female subjects

- Body Mass Index: 18.0-35.0 kg/m2, inclusive

- Subjects must not be taking drugs that are moderate to potent inhibitors of CYP3A4 or
CYP1A2.

- Subjects without clinically significant medical history in the judgment of the
investigator

- Subjects without clinically significant laboratory or ECG abnormalities

Exclusion Criteria:

- Females that are pregnant or lactating

- Administration of an investigational drug within 30 days or 5 elimination half-lives
of such investigational drug, whichever is longer, prior to study drug
administration, or planned administration of another investigational product or
procedure during the subject's participation in this study;

- Known history of treatment for drug or alcohol addiction within the previous 12
months;

- Subjects with an average alcohol intake of more than 2 units per day or 14 units per
week up to 48 hours prior to the istradefylline dose on Day 1. One unit of alcohol is
½ pint of beer (285 mL) or 1 glass of spirits (25 mL) or 1 glass of wine (125 mL);

- Donated or lost > 500 mL of blood within 3 months prior to istradefylline dose on Day
1 of Period 1;

- Positive test results for human immunodeficiency virus (HIV) or Hepatitis B surface
antigen, or Hepatitis C;

- Positive test results for drugs of abuse at screening;

- Unable, or unwilling to tolerate multiple venipunctures;

- Difficulty fasting or eating the standard meals that will be provided;

- Use of tobacco or nicotine-containing products within 90 days of the study start to
the Follow-up visit